NOAA NWS Rainfall Estimate
Reord rainfall in Fort Lauderdale. A stationary supercell thunderstorm that centered itself near Fort Lauderdale, Florida produced prolonged periods of 3+ inch hourly rainfalls creating widespread flooding. The heaviest rainfall, in excess of 20 inches, appears to have occurred from Ft. Lauderdale to Hollywood. It has been estimated that up to 1.5 inches of rain fell in 10 minutes in Fort Lauderdale!
Early on the morning of April 12th, there was a weak 1010 mb low over the central Gulf of Mexico with a slow moving warm front extending eastward to the Florida Keys. Over the northeastern Gulf surface winds were 25-35 kts from the east.
NOAA NWS Surface Analysis 1200 UTC 12 April 2023
Higher-up in the atmosphere there was a cut-off 500 mb low centered over southeastern Louisiana which was causing a strong wind flow from the WSW across South Florida. At the surface a long fetch of moderate to fresh moist ENE winds prevailed along the southeastern coast of Florida to the north of the warm front.
NOAA NWS 500 MB ANALYSIS
By mid-afternoon, the low was drifting slowly northward while the associated warm front had moved north of the Keys but was still located to the south of the Miami area. The intersection of the warm front, the strong upper-level WSW winds over moderate to fresh moist ENE winds at the surface created strong vertical wind shear with high moisture levels in the low and mid levels, an ideal environment for heavy convective showers and thunderstorms.
NOAA NWS Surface Analysis 1800 UTC 12 April 2023
A cluster of nearly stationary heavy thunderstorms developed along the Southeast Coast of Florida with the heaviest activity from Fort Lauderdale to Holiday. The combination of impervious surfaces of a highly urbanized area with extreme rainfall rates caused severe surface rainfall runoff which resulted in enhanced street flooding and flooding of airport runways.
Whether or not the rainfall amount was enhanced by climate change is debateable, however, the effects of urbanization are likely the main reason for the overall impact of the flooding.
Fred Pickhardt
